Yes, I have searched, but I can't find specific answers to these questions from those who have actually experienced the BMW PBX:

1) Will this decrease my average gas mileage by anything significant?
2) Does this put any extra wear/tear on the vehicle engine?
3) Will this work on my 328xi (AWD) model? I see it works on the i models, but what about xi?

I bought my e90 with 50k on it and I didn't know I had the BMS until 10k later when I was poking around. I then tried "tuning" on/off and the different throttle remaps, and my experience says no perceptible difference in power. It runs richer and I believe it advances the timing slightly. In my head this tells me the gas mileage should average out, which is what I noticed with the way I drive. I ended up leaving it in (lazy) but running at stock because I didn't like the throttle remap either. Too twitchy for my tastes.